yep joe has just lost his favourite jb sig les paul. and im pretty sure his will all be packed in proper flight cases. if i was you i would make sure its in the cabin with you.
If I'm flying your plane I'll throw it in the cockpit with me!!! I'll second what everyone here is saying. If the plane is a regional jet space is hard pressed and they will most likely want to gate check it in the baggage compartment. If it's a larger plane then they should be able to accommodate your guitar in the cabin.
With the bag fees the overhead bins are jam packed with everyone trying to save a buck!